Apparatus and method for watermark embedding and detection using linear prediction analysis

Abstract

In the apparatus and method for a watermark embedding and detection through a linear prediction analysis, and a record medium capable of being read through a computer having a writing of a program to realize the inventive method, in which a quality of a signal does not drop, even after an imbedding of a watermark by using a signal based on a changed shape of an original signal through a use of a linear prediction analysis, with a watermark signal to be imbedded in a digital signal, but also the watermark signal containing copyright information can be detected even though an optional attack is applied thereto.

1. An apparatus for imbedding a watermark by using a linear prediction analysis, comprising:
 a linear prediction analyzing unit for receiving an original signal and detecting a prediction coefficient predetermined through the linear prediction analysis; 
 a delay unit for receiving the original signal and delaying it by a predetermined time; 
 a linear prediction analysis filtering unit for filtering the signal delayed in the delay unit by using the prediction coefficient detected in the linear prediction analyzing unit; 
 a frequency area converting unit for converting the signal outputted from the linear prediction analysis filtering unit into a frequency area signal; 
 a psychological acoustic modeling unit for receiving the original signal and gaining a masking threshold by employing a psychological acoustic model; 
 a time-varying adaptation filtering unit for performing a control so that the signal outputted from the frequency area converting unit may have a magnitude approximate a magnitude the masking threshold gained in the psychological acoustic modeling unit; 
 a time area converting unit for changing the signal outputted from the time-varying adaptation filtering unit to a time area signal; 
 an error correction coding unit for receiving copyright information and providing an error correction function; 
 a code generating unit for providing a code to the time area signal outputted from the time area converting unit response to a signal outputted from the error correction coding unit; and 
 computing unit for adding and deducting the signal having the code provided from the code generating unit to/from the original signal response to a corresponding code, and producing a signal having an imbedding of the watermarks; 
 wherein said psychological acoustic modeling unit receives the original audio signal and obtains the masking threshold as a threshold capable of sensing audio original sound in a frequency area by employing a psychological acoustic model. 
 
   
   
     2. The apparatus as recited in  claim 1 , wherein said linear prediction analyzing unit extracts the prediction coefficient capable of predicting audio peculiar spectrum through the linear prediction analysis. 
   
   
     3. The apparatus as recited in  claim 1 , wherein said delay unit receives the original signal and delays it by a predetermined constant time, and after that, sends the delayed signal to the linear prediction analysis filtering unit, said delayed constant time τ becoming a key value in a watermark detection. 
   
   
     4. The apparatus as recited in  claim 3 , wherein said time-varying adaptation filtering unit makes an AR (autoregressive) filter on the basis of the masking threshold obtained in the psychological acoustic modeling unit, and then, performs a control so that the signal outputted from the frequency area converting unit may be passed through the AR filter and may thereby have a magnitude approximate to the masking threshold. 
   
   
     5. A method of imbedding a watermark in a watermark imbedding apparatus using a linear prediction analysis, said method comprising the steps of:
 a) receiving an original signal, detecting a prediction coefficient predetermined through the linear prediction analysis, delaying it by a predetermined time, and gaining a masking threshold by employing a psychological acoustic model; 
 b) filtering the delayed audio signal by using the detected prediction coefficient; 
 c) converting a value filtered in said second step into a frequency area signal; 
 d) AR(Auto-regressive)-filtering the frequency area signal by using the masking threshold; 
 e) converting the signal filtered in said fourth step into a time area signal; 
 f) generating an error correction code having copyright information and an error correction function, and providing a code to the time area signal according to the error correction code; and 
 g) adding and deducting the time area signal to/from the original signal according to the provided code, and producing a signal having an imbedding of the watermark. 
 
   
   
     6. The method as recited in  claim 5 , wherein in the prediction coefficient detecting step, said prediction coefficient capable of predicting audio peculiar spectrum is detected through the linear prediction analysis. 
   
   
     7. A record medium capable of being read through a computer having a writing of a program, in a watermark imbedding apparatus having a processor based on a large capacitance, said program comprising:
 a first function of receiving an original signal, detecting a prediction coefficient predetermined through a linear prediction analysis, delaying it by a predetermined time, and gaining a masking threshold by employing a psychological acoustic model; 
 a second function of filtering the delayed audio signal by using the detected prediction coefficient; 
 a third function of converting a value filtered in said second function into a frequency area signal; 
 a fourth function of AR(Auto-regressive)-filtering the frequency area signal by using the masking threshold; 
 a fifth function of converting the signal filtered in said fourth function into a time area signal; 
 a sixth function of generating an error correction code having copyright information and an error correction function, and providing a code to the time area signal according to the error correction code; and 
 a seventh function of adding and deducting the time area signal to/from the original signal according to the provided code, and producing a signal having an imbedding of a watermark.